1. Field of the Invention
The present invention relates to a refracting zoom lens system having a shake correction function.
2. Description of the Related Art
Recently, as imaging devices such as a charge-coupled device (CCD) and complementary metal-oxide semiconductor (CMOS) devices have been miniaturized, there is an increased demand for compact and slim electronic devices using the smaller imaging devices. Slim and compact cameras are classified as a slider type in which a zoom lens protrudes out of the camera body during use and is kept inside the camera body when not used, and a refraction type in which a reflector such as a prism is used so that a lens system has a reduced thickness.
However, the slider type can be miniaturized by reducing the entire length of the barrel when powered off, and thus, it is difficult to embody the slider type, which is much slimmer than a conventional camera, by using a high magnification zoom lens. Moreover, it takes a relatively long time for the slider type to move from an initial position to an operating position when the camera is powered on. In addition, a lens group that is closest to an object side protrudes out of the camera, and thus the slider type is more sensitive to impact, debris and water. Accordingly, there is a need for an optical system of a refraction type that changes the optical path. The thickness of such refraction type optical system that includes a prism can be reduced by changing the optical path of light in the middle of the optical system by 90° using a prism. Accordingly, the demand for shake correction of a compact camera is further increased.
Conventionally, the movement of an image surface, which is caused by shake occurring during photographing, is corrected using a fourth lens group. However, since the fourth lens group has a low imaging magnification, the fourth lens group needs to be moved significantly in order to correct for the shake. Thus, the resolving power of an imaging device can be reduced. Accordingly, in order to maintain the resolution of an optical system, the configuration of the lens groups becomes complicated and the number of required lenses is increased.